Unraveling Triple-Interface Evolution in Li-Rich Mn-Based All-Solid-State Batteries

Integrating high-capacity lithium-rich manganese (LRM)-based cathodes into all-solid-state lithium batteries (ASSLBs) presents an alternative strategy to improve the energy density and safety. In this scenario, the dual-electrolyte system with a sulfide–halide composite configuration has been widely proven feasible. However, the compatibility issue at the LRM/halide/sulfide triple interface has severely hampered the practical implementation of ASSLBs, with the underlying interfacial evolution mechanisms yet to be fully elucidated. Herein, we comprehensively attempt to understand the triple-interface alteration by manipulating different upper cutoff voltages. Multiple in/ex situ characterizations validate that lattice oxygen evolved from LRM penetrates the Li3InCl6 (LIC) layer to react with Li9.54Si1.74P1.4S11.7Cl0.3 (LSPSC), inducing InS–, LiCl, and SOx– formation, thus exacerbating the interface stabilities of both LIC/LRM and LIC/LSPSC at 4.6 V. By comparison, under a voltage of 4.4 V, the accumulation of In–O/S bonds is obviously alleviated, which enhances Li+ transport kinetics between LRM and LIC. Furthermore, the intensities of S–S and P–Sn–P are also relieved, which further demonstrates that the parasitic reaction of LIC/LSPSC is significantly suppressed. Therefore, the prepared cells achieve a high discharge specific capacity of 258.72 mAh g–1 at 0.1 C at 2.0–4.8 V and good cycle stability with a capacity retention up to 74.6% after 200 cycles at 0.5 C at a voltage of 2.0–4.4 V. This work underscores the significance of cutoff voltage modulation in inhibiting interfacial degradation, thereby providing new insights into constructing stable interfaces in the LRM-based ASSLBs.